Process and device for direct production of steel from iron-containing materials

ABSTRACT

Process and device for direct continuous steel production out of iron-containing materials using usual power coals as fuel and reducer. It is provided to carry out the process in a single reaction space comprising a layer of liquid refining metal present under a layer of liquid slag comprising iron-containing materials to be processed and droplets of reduces metal so that an intermediate emulsion layer “slag-gas-metal” is designated in between the said layers. In an upper slag layer fuel is burnt and finely grained iron-containing materials are reduced according to coke-free technology of cast-iron production with carbon content at the level of ˜4.5-4.8%; iron oxides and reduced metal droplets are transferred from slag layer into intermediate emulsion layer; iron oxides are decomposed and oxygen is isolated together with oxygen-containing gas supplied to emulsion layer. Refining process proliferates to lower refining layer and carbon oxide isolated during refining stimulates reduction processes in slag layer. Basic structure of the device with single reaction space can be adapted to different technological problems and peculiarities of properties in iron-containing materials processed. The solution proposed permits to obtain steel with carbon content within the limits of 0.2-2.0% and with permissible content of admixtures having specific productivity of the device up to 2.0-2.5 t/m 2  of bottom per hour and productivity of a single unit equal to 50,000-5000 000 t/year.

FIELD OF INVENTION

The present invention related to the field of metallurgy, to ferrous metallurgy in particular, and is destined for direct continuous steel production from non-agglomerated iron ore, iron ore concentrates, iron containing waste and other iron-containing materials.

BACKGROUND OF THE INVENTION

Steel production is usually based on two main production stages:

-   (1) iron reduction from iron containing materials and production of     iron-carbon product—cast iron with relatively high carbon content. -   (2) refining of the iron-carbon product—cast iron obtained with the     aim of decreasing carbon content and admixtures up to the determined     limits and producing steel.

Previously, the first stage was usually performed by melting in the blast furnace where high quality metallurgical coke is used for iron reduction from oxides. The invention proposed relates to performing this process in the bubbled slag melt using elements of modern coke-free reduction processes where usual (so called power-generating) coal is used as a reducer instead of coke for processing iron containing materials. Second stage—refining—is carried out in a separate device, e.g. converter for refining iron-carbon product and producing steel. Notion “iron containing materials” includes such materials as grained iron-containing ores, iron ore concentrates, iron-containing scrap, iron-containing waste, etc. Notion “refining” means decarburization and removal of other admixtures present in carbon iron intermediate product, up to the values determined.

Main principles for implementing the processes of coke-free iron reduction in bubbled slag melt are rather well known and do not necessitate detailed description.

As for the second stage, converting is a periodic process requiring separate equipment, thus characterizing the first essential drawback of this stage. The other drawback of the converting process consists in the fact that the oxygen flow delivered into the melt, reacts with carbon and simultaneously partially oxidizes iron turning it into slag. In this case quality steel output out of iron-containing materials is sure to become lower.

Implementation of the modern technology for steel production as two subsequent operations (stages) in two independent metallurgical plants possesses one more rather important drawback—an economical one: steel production cost is sharply increased due to application of two independent devices.

All the above said is certified by the known technologies and plants protected by patents and using bubbled slag melt where the operations of reducing the main component, e.g. iron from iron oxides are performed when producing different metals, alloys and semi-products, or, on the other hand, operations of refining, e.g. oxidation of reducer (carbon) residue and admixtures in cast iron melt are carried out in such a way that their content doesn't exceed permissible values in the end product obtained,—see, for example, sources [1]-[17].

Patents [1, 2, 4, 5, 6, 8, 9, 16] can be united into one group with a common distinguishing feature consisting in subsequent metal reduction from oxides, e.g. Fe reduction in Romelt furnace out of FeO and Fe₂O₃ in accordance with patent [16]—U.S. Pat. No. 4,913,734—where reduced metal enters independent plants for refining, e.g. converters, electric furnaces or other installations.

Such mating of Romelt furnace with refining installations somehow shortens the time of additional metal heating, but doesn't exclude the necessity of this operation: refining is carried out in semi-continuous regime, necessitates separate maintenance and, hence, additional expenditures.

Sources [5, 6, 8] contain the description of an installation (furnace) and complex plant on the basis of Hismelt furnace for conducting reduction processes.

Distinguishing feature of this process consists in supplying processed raw material and fuel (reducing agent) together with blast by means of tuyeres installed on vertical walls in the same way as in Romelt process; the structure of gas duct system permits to use the heat of effluent gases for heating processed charge and partially returns undesirable exhausts back to the furnace.

Pilot exploitation of the installation developed has shown its high reliability; the installation was operable 99.8% of working time. At present company Hismelt is building a big industrial installation on the basis of the installation mentioned.

Patent [10]—U.S. Pat. No. 5,480,474—provides for liquid-phase reduction of preliminary prepared iron-containing material by using solid carbon for cast iron production with low carbon content. The furnace has two reaction chambers situated close to one another, but at different levels, their reburning zones being connected by an inclined pipeline. Reduction is carried out in a larger chamber, while in a smaller one the emulsion is divided into slag and metal with simultaneous partial oxidation of carbon residue in metal. Oxygen is supplied by vertical moving tuyeres into both reaction chambers. Distinguishing feature of the installation described consists in the fact that effluent gases and partially slag are returned to the first, larger reaction chamber. However, with the reaction chambers layout applied it seems doubtful to obtain effective mass- and heat-transfer between reacting masses “slag-metal” in larger and smaller reaction chambers and to get sufficiently high carbon oxidation in metal produced.

Patents [11] and [12] protect “trough type” installations for Fe reduction and refining cast iron obtained from carbon. Installation for Fe reduction is mounted in the first part of the trough and then, melted Fe moving along the trough enters the installation for carbon refining. Thus, these installations seem to describe allegedly “direct” steel production out of iron-containing raw material.

Though in practice, these installations differ from those described in patents [1, 2, 3, etc.] only by method of metal transportation from reduction zone to refining zone; from the economical point of view they represent two independent installations working in series with their separate expenditures which are simply summarized.

Patent [13] protects a furnace having highly effective medium for melting and purification of steel scrap isolated from gas by slag layer actively mixed by burning gas flows.

Invention according to patent [14] differs from patent [10] discussed above only in having independent devices for supplying solid materials and gas flows as well as for discharging gases and melts from or into two reaction chambers installed at one level; a partition is installed between chambers permitting the melt to flow in desired direction.

The authors of the invention recommend to conduct metal reduction out of oxides in one reaction chamber, while the second can be used for oxidation refining.

Patent [16] protects Romelt process of liquid-phase reduction of Fe out of melt containing FeO and Fe₂O₃ which was described earlier. Further development of this invention is given in patent [9]—Nippon Steel. This patent protects installation of Romelt furnace together with two continuous installations connected in series for refining cast iron obtained from carbon and sulfur. Company Nippon Steel developing the installation Dios paid a lot of attention to the problem of increasing productivity of a single furnace. It is known that Romelt furnace productivity is limited due to rectangular cross-section accepted. Nippon Steel proposes an interesting solution in patent 20.

A furnace with bubbled slag melt for processing copper-containing materials has been protected for the first time by a patent [17] issued in the name of prof.A.Vanyukov. This patent served as starting point for development and introduction of coke-free metallurgical processes in bubbled slag melt.

In conclusion it is to be noted that in description to patent [3] problems of controlling Romelt process are considered. Hereby, patent [3] deals with only the problem of stabilizing the regime of Fe reduction out of FeO and Fe₂O₃. It represents only a small part of control problems which are to be solved during “direct” steel production out of iron-containing raw material.

Summarizing the analysis of patents protecting different metallurgical processes with bubbled slag melt, it should be noted that they present either carrying out separate metallurgical operations in one technological installation, or subsequent processing of initial products in two or more independent technological installations (vessels), i.e. when one of end products in one installation, e.g. melt, serves as initial product for subsequent installation.

Hereby, no patents have been found protecting carrying out several independent operations in a single reaction space with functionally different technological zones, whereas this unification improves feasibility data of production on the whole.

According to patent research it appeared that among the multiplicity of technologies developed in different countries of the world, the leading place in development of ferrous metallurgy has been taken by melting in slag or metal melts bubbled by oxygen-air blast (Russia, USA, Japan, etc.).

Such reaction medium has been used for the first time by Prof. A.Vanyukov (Russia, patent [17]) for melting copper-containing raw material. For more than 20 years all copper raw materials are being treated in such furnaces in Russia and a number of other countries obtaining rather high feasibility data.

In the middle of the 1980s prof.V.Romenets et al. (Russia, patent [16]) proposed Romelt process for direct reduction of iron from the raw material mentioned above by using usual coals; during 1985-1994 this process has been mastered at Novo-Lipetsk Metallurgical combine. When mastering the process more than 20,000 t of cast iron has been obtained having carbon content of 3.8-4.8% which was further processed in converter for steel. The process has been patented and sold to company Nippon Steel (Japan) and company Kaiser (USA) on all the territory excluding Russia and India; construction of metallurgical plant in India [16] is going on based on this technology.

Romelt technology as well as Hismelt, Dios and others known in the world, doesn't permit to decrease carbon content in metal obtained lower than ˜3.5.-4.0% and produce steel. That's why in order to obtain steel after Romelt furnace, the plant under construction in India is going to be equipped with technological plants used at present for cast iron refining.

Due to the above said, there appeared an idea of further exploration of the direct iron reduction process in developing a new technology of cast iron refining which can be combined with modern reduction technology in a single reaction space and will permit to obtain steel directly with carbon content within the limits of 0.2-2.0% and permissible admixtures content.

When mastering the process of liquid-phase reduction Romelt at Novo-Lipetsk Metallurgical Combine (NLMC) critical phenomena occurred several times characterized by boiling and emergency outburst of metal (cast iron) produced from furnace metal collector. Carbon content in this metal, however, dropped from ˜4.5-4.8% typical of cast iron to ˜1.0-2.0% typical for steel.

Studies in Romelt furnace special behavior under critical conditions suggested the possible approach for attaining stable decrease and maintaining carbon content in the metal obtained within the required limits. This permitted to outline the strategy for developing the new technology for conducting reduction and refining processes in a single reaction space of one technological installation.

Hence, the aim of the invention proposed consists in developing such technology (process) of carbon iron product refining which can be carried out together with iron reduction technology in a unified reaction space and which permits to produce steel directly with carbon content within the limits of ˜0.2-2.0% and permissible admixtures content. The natural second aim of the invention consists in developing a device (installation) as well for implementing the technology mentioned.

SUMMARY OF THE INVENTION

The goal set forth is attained by means of the proposed process (method) and device (installation) for its effectuation.

For conducting the process of direct steel production according to the present application for patent, the structure of a single reaction space is being proposed, where refining (R)-subspace is positioned down under melting-reduction (MR) subspace.

Exchange of flows containing reduced metal droplets, slag and gas between both subspaces is performed through intermediate slag-gas-metal emulsion layer (IEL) situated in between them.

(Such layout principally differs from known analogues described above, where separate technological zones are positioned, mainly, horizontally and are practically always separated from one another by partitions at least, providing for almost independent performance of technological operations in each zone, i.e. absence of connection between almost all flows taking part in the technological process serves as a characteristic feature).

Let us study a more detailed description of the reaction space structure patented and operations conducted in each technological subspace, as well as in intermediate emulsion layer (IEL) in the reburning zone.

In the “upper” MR-subspace of the basic adaptive structure of the device reaction space, operations of solid fuel burning, charge melting and reduction of iron and admixtures for obtaining intermediate product—cast iron—in bubbled slag melt are carried out; depending on raw material processed, MR-subspace can be divided by a partition into two operation zones—melting and reduction ones. For example, such necessity appears when processing finely grained (100% −20 mm) iron-containing ore or scrap.

In MR-subspace, above the bubbling slag, a reburning zone is functioning for gases isolated during raw material melting and iron reduction, these gases being further delivered to the systems of heat utilization and ecological purification of effluent gases before their discharge into atmosphere.

In the “intermediate” zone, in intensively mixed intermediate emulsion layer (IEL-layer) “slag-metal-gas” the process of reduction is continuing, but, due to rather high concentration of metallic phase and intensive mixing, active interaction between droplets of intermediate product (cast iron) entering the zone from MR-subspace, non-reduced FeO from slag and oxygen occurs simultaneously, as well as transfer of these products into R-subspace. Flow of gases obtained during refining and containing mainly carbon oxide F(CO) is inversely transferred from R-subspace into MR-subspace for application during reduction of material under processing (iron oxides).

IEL layer practically performs the function of positive feedback for the lower zone—R-subspace as mixing intensity in IEL layer depending mainly on F(CO) to a great extent determines oxygen supply for refining and intensity of the process.

Metallic phase goes to refining while slag emulsion containing metal is discharged from the intermediate zone into a settling zone where from, after separating, slag is discharged from the system and settled metal returns back into the lower layer of metal.

In the “lower” zone intermediate product is refined and brought up to determined requirements in relation to technical characteristics.

In this case the central problem concerns choice of R-subspace structure in accordance with the special physico-chemical content of iron-containing raw material processed and given determined characteristics of steel to be produced. Refining process can be carried out as a one-stage process in the “lower” refining layer by acting directly with “intermediate emulsion layer” and “upper” layer. In case of necessity two-sage refining with slag change is possible. First preliminary stage includes desiliconization, desulfuration, and partial decarbonization, while the second stage is the continuation of the refining process and preliminary bringing up to the level. In case of necessity the product goes for out of furnace processing for obtaining final determined characteristics.

Further, let us study the main stages of the proposed process in more detail.

In the “upper” zone iron-containing materials to be processed, slag components, solid carbonic fuel and oxygen-containing gas are continuously supplied. Oxygen of the entering gas provides for burning part of fuel with isolation of heat which is used for melting solid materials supplied and maintaining the determined heat regime. The rest of fuel is used for reduction of metal oxides contained in iron-containing materials charged and formation of liquid melting products—slag and intermediate carbon iron product.

Two schemes of solid carbonic fuel supply are considered. The first one uses charging of all fuel into the “upper” zone from above, and the second scheme relates to screening small fractions and blowing them at the lower boundary of the “upper” zone, while large fractions are charged into the “upper zone” from above.

Processes of charge melting and reduction in MR-subspace can be divided from each other by partitions. In this case flows of fuel (reducing agent) and oxygen-containing gas are divided correspondingly. Hereby, small fractions of carbonic fuel are mainly used for melting, and small ones—for reduction.

Oxygen-containing gas flows supplied to the upper zone provide for bubbling of the melt with the aim of intensifying the process of heat- and mass-transfer during melting and reduction.

The melt further goes to intermediate emulsion layer, and technological gases formed during fuel burning and reduction are going to reburning zone situated within the limits of the upper zone directly over the bubbling melt.

Technological regime of the upper zone determines the degree of iron oxide and admixtures reduction as well as carbon content in the slag which reaches intermediate emulsion layer.

In the “intermediate” zone, within the limits of the emulsion layer, continuous, intensive turbulent-diffusive mixing is carried out as well as the transition of the products mentioned before. Transition intensity depends on the flow of iron-containing intermediate product droplets and the slag flow, as well as on effluent gases entering from the refining zone and flows of additionally supplied oxygen or/and oxygen containing gas and/or inert gases supplied through side and/or bottom tuyeres.

Coefficient of turbulent-diffusion transfer Dslme together with changing surface of intermediate emulsion layer Sslme and the content of reduced and oxidized iron in it, determines to a great extent the productivity of the technological installation and quality of steel. The question will be further studied in more detail.

In the “lower” zone effectiveness in refining carbon iron intermediate products and production of the determined carbon and admixtures content in steel practically depends on the R-subspace structure chosen and organization of technological process in all the reaction space, as a sufficiently large quantity of oxygen for refining enters with non-reduced iron oxides contained in slag.

The application covers two structures of R-subspace organization with one-stage and two-stage refining and two regimes for both structures: first, when oxygen enters with Fe oxides and in the form of directed jets at the level of intermediate layer lower boundary (variant with upper blast) and the second, when bottom supply of oxygen and/or CO₂ and/or air, and/or inert gases, and/or their different mixtures (variant with combined blast). Combined blast permits to realize technological regimes with higher specific productivity and lower fuel consumption. During one-stage refining, the steel obtained is mainly discharged from the lower zone and in case of necessity goes to out-of-furnace processing and refining according to the given regulations before casting.

Waste slag from the settling zone is discharged through a siphon drain.

During two-stage refining with direct metal and slag flow the main part of slag is discharged from the system after the first stage; new slag being delivered for the second refining stage. Metal and slag discharge from the second stage of refining is conducted in the same way as in the case of one-stage refining. With counter-flow of metal and slag, slag direction is changed only during the second stage; metal and slag discharge is carried out from different ends of the second stage; in this case the scheme described for one-stage discharge of metal produced and slag obtained is used.

Let us present the most important propositions characterizing the technology(process) subjected to patenting in more detail. In the upper subspace melting of processed iron-containing materials and iron and admixtures reduction takes place. Reduction of iron oxides takes place according to chain mechanism; carbon dioxide CO₂ obtained in this zone during carbonic fuel burning causing the appearance of this chain.

Drops of reduced intermediate semi-products from the upper zone and non-reduced iron oxide contained in slag enter the intermediate actively agitated emulsion layer. Iron oxide interaction with reduced metal starts leading to oxide decomposition for ions of iron and oxygen. Due to ions of oxygen formed in metal, decarburization reaction of the semi-product produced during reduction starts leading to decrease in carbon content corresponding to determined characteristics for steel production. This process is continued is the lower refining subspace.

As the result of the decarburization reaction carbon oxide isolation takes place which increases agitation in emulsion layer; coefficient of turbulent-diffusion transfer and interphase surface in emulsion layer are growing, thus leading to increase in the speed of occurring chemical reactions and increase in oxygen delivery. Speed of decarburization processes increases and metal “boils”. Metal refining from admixtures is also intensified.

The cycle described represents nothing else but the cycle with “positive feedback”. Positive feedback in decarburization process maintains refining regime in one of the attractive fields of the bi-stable dynamic system—“emulsion layer—refining subsurface” permitting to obtain carbon content in metal 0.2-2.0%. Thus, by maintaining the desired quantity of oxide in the melt, continuous refining successfully leads to steel production.

It is preferable that pre-determined content of carbon and admixtures in steel produced can be maintained or corrected, in case of necessity, by changes in the flows of solid carbonic fuel supplied and/or by the flow of charge processed and/or oxygen-containing blast flows.

Refining process can be carried out continuously or by forming a definite type of oscillation process inside intermediate emulsion layer and refining layer. This oscillatory process considerably intensifies mass transfer in the process of decarburization.

Iron oxide, oxygen and carbon content is periodically checked and corrected for maintaining the working regime. When reaching the necessary working regime it is desirable to partially substitute bottom supply of oxygen-containing gas by inert gas supply, e.g. by argon or other gas.

The described mechanism of the process for obtaining semi-product (cast iron) and producing steel has become possible due to the structure of a single reaction space.

BRIEF DESCRIPTION OF THE DRAWINGS

The essence of the invention and necessary details of the process proposed and devices for its realization are explained by the drawings attached where:

FIG. 1—Basic adaptive structure of single reaction space for direct steel production out of iron-containing materials.

FIG. 2 a—“Phase surface” of interconnection between carbon and oxygen content in the lower refining furnace zone for direct steel production out of iron-containing materials (T=1600° C.).

FIG. 2 b—Transition process from representative point 01 (cast iron) to representative point 02 (steel).

FIG. 2 c—Change in variables of the “upper” and “lower” furnace zones in the process of regime transition from intermediate (cast iron) product production to direct steel production using oxygen from FeO.

FIG. 2 d—Change in variables of the “upper” and “lower” furnace zones in the process of regime transition from cast iron and steel with C=0.5% up to steel production without using pulse controls (combined blow-down).

FIG. 2 e—Change in variables of the “upper” and “lower” furnace zones in the process of regime transition from cast iron and steel with C=0.5% up to steel production by using pulse controls (combined blow-down).

FIG. 3—Furnace for direct steel production out of fine grained iron-containing materials (transverse section).

FIG. 4—Furnace for direct steel production out of fine grained iron-containing materials (longitudinal section—one stage refining).

FIG. 5 a—Furnace for direct steel production out of fine grained iron-containing materials (longitudinal section—two stage refining).

FIG. 5 b—Furnace for steel production out of fine-grained iron-containing materials with external refining block (longitudinal section—two stage refining).

FIG. 6 a—Auxiliary side tuyere for gases and solid powders supply.

FIG. 6 b—Drawing of a partition with cooling heat tubes.

FIG. 7—Changes in variable with pulse interruptions in fuel supply.

FIG. 8—Changes in condition variables and incoming flows with durable furnace shut-down and after transition to stationary regimes of steel production.

FIG. 9—Changes in condition variables with furnace transition for steel production without forestalling bottom oxygen feed (FIG. 9 a) and with additional bottom feed (FIG. 9 b).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Two basic principles

-   -   presence of two equilibrium states in the process of refining,         in the given implementation of the process (FIG. 1), within the         real region of variables changing and     -   the method of refining process transition into the desired         equilibrium state providing for the possibility of direct steel         production,—have determined the basis of the method o for direct         steel production proposed for patenting.     -   First, we are going to show (it is done by the author of the         invention proposed for the first time) how, during the process         of refining carbon iron intermediate product, condition         providing for quick transition of refining process from         equilibrium state with coordinate 01 corresponding to carbon         iron product with carbon content C=˜4.4.% to the second         equilibrium state with coordinate 02 within the range         C=˜0.2-2.0%.

For higher justification of choosing the strategy mentioned, let us briefly consider the essence of phenomena occurring during refining of carbon iron intermediate product (cast iron) obtained during reduction and making the basis of the technology patented.

Let us imagine that the incoming flow of intermediate product droplets FmeO entering refining zone and outgoing metal flow (steel) Fme from that zone with stationary regime differ in a general case for values of oxidized carbon C, reduced iron Fe and admixtures. We continue considering peculiarities of dynamic properties of refining process only using the example of carbon behavior as the main component of admixtures to be removed.

Entering flow of carbon Fmec=FmeO*CmecO, where

FmeO is the flow of reduced semi-product,

CmecO—current carbon concentration in this semi-product after refining,

M—metal mass in refining zone,

Cmec and CmeO—current concentrations of C and O in metal mass M, present in the refining zone of steel produced.

Output flow of carbon Frmec=(Fme*Cmec), where

Fme—outcoming steel flow.

Metal decarburization occurs as the result of interaction between Cmec and CmeO dissolved in the metal mass M.

Let us present the system of equations describing main bond between incoming flows, outgoing flows, condition variables (Cmec and CmeO) and metal mass M in continuous refining process for representing the process as a model of “ideal mixing”. Without specifying the technique of other flows input which contain oxygen and/or carbon dioxide and/or inert components into the refining zone, let us write down the equation describing the process: Cmec′=(1:M)*((Fme0*Cmec0)−(M1mc*FV1meo)−(Fme*Cmec))   (1) Cme0′=(1:M)*((Fme0*Cme0)−(FV1meo)−(Fme*Cme0)) where

M1mc—ratio of molecular weight C:O during refining,

FV1meo=K1*((100*Cme0)−(C0rav)), where

C0rav=((0.0035:Cmec)+0.004)−equilibrium between C

O in boiling (bubbling) metal during refining [18],

K1—macro-constant of reaction rate;

In relation to the task set forth, we are to consider a scheme with effective oxygen income into metal to be refined through intermediate emulsion layer “slag-gas-metal”. Then, additional supply of oxidizing gases mentioned above into intermediate emulsion and refining layer is to be discussed during patent description, as well as possible schemes of gases supply.

The rate of refining process is determined in the given case mainly by oxygen flow entering the metal to be refined from slag: Fpmo=K2*Dslme*((a(FeO)*Krasp*Cslfeo)−Cme0)*Sslme where:

K2—constant,

Dslme—coefficient of turbulent-diffusion transfer,

Sslme—interphase surface of intermediate layer,

a(FeO)—coefficient of FeO activity,

Krasp—distribution constant,

Cslfeo—FeO content in slag at the boundary with intermediate layer.

Effect of metal “self-boiling” well known for specialists in metallurgy, e.g. in the process of bottom decarburization during open-heath process or converter refining, is considered as the heart of the process.

For the given layout of the process, the connection of the coefficient of turbulent-diffusion transfer Dslme and interphase surface of metal to be refined Sslme with flow Fco obtained during refining and leaving this zone is to be written in the following form: Dslme=kd*(Fco) Sslme=ks*(Fco)

Let us approximate dependencies Dslme=kd*(Fco) and Sslme=ks*(Fco) by a “step-like” function, e.g. “arctg”.

Correspondingly, let us consider the system condition as a “calm” one in case Dslme=Dslme-min and Sslme=Sslme-min, and as a “boiling” (bubbling, active) one in case Dslme=Dslme-max and Sslme=Sslme-max; ratios (Dmax:Dmin) and (Smax:Smin) can be rather big. Dependence of coefficients Dslme=kd*(Fco) and Sslme=ks*(Fco) on CO flow practically represents the effect of a positive feedback.

Let us introduce designation Fpo2 for the flow of oxygen or other gas additionally supplied into metal M to be refined in the zone of contact with intermediate emulsion layer for charging powder-like reagents, elimination of delay in the process furnace transition for steel production and in case of other industrial problems. Flow Fpo2 is added to flow Fpmo.

Let us study the peculiarities of state variables movements in the bath with carbon iron product to be refined which are described by a system of differential equations (1). Taking into account essentially non-linear character of the system (1) and low order, let us apply the method of “phase surface” or “phase space” in case of non-isothermal regime.

FIG. 2 a shows the example of phase portrait of interconnection between the two state variables - carbon content Cmec and oxygen CmeO in refined melt under non-stationary isothermal regimes and normal functioning of the furnace. The portrait has been obtained for refining temperature 1600° C. FIG. 2 a shows carbon and oxygen content in metal in shares. That's why. for transition to percentage at the axes scale coefficients are given. Equilibrium state 01 with C content ˜4.4% corresponds to cast iron production, and second state 02 with C content ˜0-0.2-2.0% corresponds to steel production. Each of equilibrium states acts as an “attraction” center for its regime, what is well seen according to system movement trajectory in the vicinity of each condition. Between the “attraction” sites mentioned in the vicinity of points O1 and O2 there exists a boundary which hinders the transition from one “attraction” site into another. That's why the technological process occurring in attraction site of point O1 and producing cast iron never enters site of point O2 where steel can be produces or vice a versa without applying special external actions.

Analysis of equation system (1) shows that the refining process studied as a dynamic object possesses the following properties:

a) refining process is characterized by more than one equilibrium state,

b) It is possible to provide for the desired positioning of at least two sites with stable equilibrium state—one for “calm” and the other for “boiling (bubbling)” metal—by choosing the corresponding technological regime and parameters of furnace design with the aim of obtaining real parameters of the process for refining intermediate carbon iron product (cast iron); in this case the sites mentioned are divided one from the other by a limited intermediate region—theoretical boundary line.

The model proposed is good for reproduction and explanation of phenomena which appear with critical situations occurrence in Romelt process.

c) with any ratio o technological and design parameters it is impossible to get stable movement in the vicinity of all the equilibrium conditions;

It has been mentioned earlier that it is necessary to overcome an intermediate region which is equivalent to energy barrier in order to transit from producing one kind of metal to the other.

This means that in case it is possible to find methods of overcoming the said barrier and to obtain system transfer from equilibrium state O1 to state O2 within the normal technological regime, then it would follow that instead of cast iron production, steel production can occur. It should be noted, that overcoming the energy barrier can be more effectively achieved not by using continuous control but by means of short-time pulse actions—only during technological regime transition from one equilibrium state to the other. Changes in solid carbonic fuel flow and flow of charge to be processes as well as, to a limited extent, changes in oxygen or oxygen-containing gas flow supplied to the metal to be refined in such a way that they don't disturb the hydrodynamic of the process, can be used as pulse actions.

Positive feedback described earlier facilitates process transition into equilibrium condition “steel”.

The research conducted permits to use sufficiently greater volumes of oxygen in FeO present in slag for conducting the refining process and at the same time to considerably decrease iron oxide content in discharged slag, to increase total content of isolated iron, to decrease the quantity of oxygen supplied from outer sources.

Further, we are going to consider specific problems of the furnace starting and operation with direct steel production.

With direct steel production specific problems of furnace starting and operation are being solved.

First, let us study the appearance of the main problem of starting furnace for steel production.

The furnace is cold, all the mechanisms providing normal functioning of the furnace have been tested. Possibility of normal starting draft and blast devices, heat exchange systems, supply of blast, solid carbonic fuel and iron-containing material to be processed and flux have been checked. All the service mechanisms and instruments are in working condition. The furnace is ready for being started. Two different starting technologies are being considered:

-   -   first technology with preliminary slag and melt production on         the basis of cast iron and     -   second technology with preliminary slag and melt production on         the basis of steel.

The main difference between the technologies lies in the fact that after the end of preparatory period before transition to the normal functioning regime, the metal charged according to the first technology has carbon content ˜4.5-4.8%, while with the second, the carbon content is mainly not more than ˜1.0-2.0%.

First variant of starting technology for cast iron production:

-   -   iron-containing material and solid carbonic fuel are charged         simultaneously into the furnace.     -   oxygen containing gas is supplied simultaneously with charging.     -   fuel oxidation and heat isolation start.     -   iron-containing material and flux start melting; in this case         due to excess of the fuel supplied process of reduction starts         up producing liquid melting products—slag and intermediate         carbon iron product (cast iron).     -   discharging of slag, melt obtained and technological gases         formed during melting is carried out. Adjusting of technological         regime starts.

Second variant of starting for cast iron production:

-   -   iron-containing material and solid carbonic fuel are charged         simultaneously into the furnace.     -   liquid slag obtained during production of ferrous metals (e.g.         in electric furnaces) is poured into the furnace (cast iron or         any other iron-containing melt on the basis of cast iron can be         used),     -   last stage from the first variant of starting is repeated (i.e.         output of slag, melt obtained and technological gases),         adjustment of technological regime is carried out.

Third variant of starting for cast iron production:

-   -   slag melt is formed by loading and melting solid oxide materials         or their mixtures, e.g. blast, open-hearth, converter and other         slags, metal oxides—CaO, MgO, SiO₂, Al₂O₃, etc. into the         furnace,     -   oxygen containing gas is supplied above the melt surface,     -   supply of solid carbonic fuel is started,     -   last stage from the first variant of starting is repeated.

The variants of the furnace starting discussed practically use the method of furnace starting Romelt used for cast iron production. It is only the starting stage for the technology of steel production as in this case melt with carbon content ˜4.5-4.8% is obtained. After that the main stage of furnace transition for steel production starts when carbon content is decreased to ˜0.2-0.3% or other given value. After attaining the carbon content and admixtures level desired the regime is sustained; usual furnace operation starts.

It is possible to start furnace for direct steel production, but this method is much more complicated as it necessitates carrying out all the starting operations at higher temperatures and, what is most important, doesn't permit to carry out stationary regime preliminary adjustment when producing cast iron.

Let us study the method of starting the furnace with one-stage refining for “upper”, “bottom” and “combined” blast (for steel production). So, according to one aspect of the present invention, the second operational stage in the technology described should provide for changing the carbon content in the melt from ˜4.5% to the determined one in steel to be produced and for further maintaining this content at the predetermined level.

The first, main substage is to decrease of carbon content in molten metal in the furnace up to a predetermined C content (˜0.2-0.3%) with the aim of further furnace transfer for stationary regime.

With specific steel productivity up to 1 t/m² of bottom per hour, the application proposes to use mainly oxygen from FeO in slag according to the scheme equivalent to “upper” blast. Small addition of oxygen or oxygen-air mixture flow is necessary for supplying reagents in the metal layer to be refined.

The first method proposed permits to continuously control the flow of incoming air by means of pulse interruption (decrease) of continuous flow of solid carbonic fuel entering the furnace.

Pulse interruption in solid carbonic fuel supply into operating furnace causes equivalent pulse (sharp) increase in FeO in the intermediate emulsion layer “slag-refined metal” and equivalent changes in oxygen supply from slag.

By sending several pulses interrupting fuel supply in the interval of up to 5-6 hours, it appears possible to carry out transition of technological process from regime 01 with production of intermediate product (cast iron) to regime 02 with steel production. In this case carbon content in the metal obtained decreases gradually up to the determined level which is further maintained by the systems of automated control.

FIG. 2 b shows the trajectory of a representative point transition from initial state 01 under the action of the first pulse to point 02.1 which is situated in the attraction field of a special point 02. Then, due to positive feedback functioning as well as other pulses, the process along a complex trajectory transfers into point 02 corresponding to steel production and further remains in the permissible vicinity of this point. Scale in FIG. 2 b is analogous to that in FIG. 2 a.

FIG. 2.c gives an example of furnace transition for steel production by sending only two or three pulses interrupting fuel supply. The experiments have been carried out with specific load of 1.0 t (m² of bottom per hour).

Identified mathematical model of the process has been used during research [19].

Transition process equals to 5 hours with sending two pulses each, e.g., 20 minutes long with an interval (period) between pulses equal to 50 min. and amplitude (0.95*Fpy). Carbon content in steel obtained equals to ˜0.2%. Fpy means charged fuel rate.

When sending three pulses 15, 20 and 15 minutes long with interval between pulses equal to 60 min, the length of transition period and carbon content in the end have not changed, however, the amplitudes of FeO content in slag have changed during transition period. This is very important for furnace stable functioning. It is rather important for stable functioning of the furnace.

It is also necessary that the amplitude peaks don't exceed the range +1.0% and −5.0-6.0 of FeO content in the slag.

Research has shown that in case process transition from producing intermediate product to steel production is effectively organized, then real average metal output during transition period decreases insignificantly (it is not shown in curve 8 in FIG. 2.c).

FIG. 2 c gives the following conventional designations and value dimensions which permit to calculate the values of all physical values according to data obtained in chart with dimensionless units. To obtain that it is necessary to divide the values obtained by value coefficients; dimensions of physical values obtained and time in hours in all the graphs are the same for the given patent application. Value dimensions for recalculation may differ one from the other.

FIG. 2 c gives the following conventional designations and value dimensions:

Upper Zones

-   {circle around (1.)}Fsh=Fvsh: 0.000005.—charge consumption -   {circle around (2.)}Fpy=Fvy: 0.00001—fuel consumption -   {circle around (3.)}Cslfo=Cvslfo: 1—FeO content in bubbled slag -   {circle around (4.)}Cslco=Cvco: 0.1—CO content in gases -   {circle around (5.)}Cslco2=Cvco2: 0.1—CO₂ content in gases -   {circle around (6.)}Cslc=Cvslc: 1—C content in slag -   {circle around (7.)}Csl1fo=Cvs11fo: 1—FeO content at the border with     emulsion layer -   {circle around (8)}T=((Tv:0.0001)+1000)—Temperature of bubbled slag

Lower Zones

-   {circle around (1.)}Cmec=Cvmec: 1—C content in metal -   {circle around (2.)}Cme0=Cvme0: 10—oxygen content in metal -   {circle around (3.)}Fpmo=Fvmo: 0.00004—oxygen supply -   {circle around (4.)}FV1meo=Fvmeo: 0.00004=oxygen consumption -   {circle around (5.)}Csl3fo=Cvs13fo: 1—FeO content at the border with     emulsion layer -   {circle around (6.)}T3sps1=((Tv3:0.0001)+1000)—slag temperature -   {circle around (7.)}Tme=((Tvme: 0.0001)+1000)—metal temperature -   {circle around (8.)}Fme=Fvme: 0.00001—flow of produced iron

Values containing index “v” (e.g. Cvco) are shown in graphs FIG. 2 c.

Regime with production of low-carbon product or steel can be maintained as long as necessary in case there won't appear any disturbances in the furnace able to interfere with the regime and cause the necessity of returning to sending intermittent pulses; the number of pulses fully dependent on the disturbance occurred.

When studying FIG. 2.c let us pay attention to the following:

First—presence of considerable lag when transmitting signals after sending pulses from MR-subspace to R-subspace; time lag attains 0.5 hour and more.

Second—occurrence of lowering carbon content in slag melt at the moment of maximum amplitudes of pulses applied which are higher than maximum permissible ones in the given experiment. With such drops in carbon content changes in direction of main reduction reaction for a reverse one have been observed which are highly undesirable.

Elimination of time lag and ability of even short time change in reversible reaction of Fe reduction can be attained by using combined blast.

FIG. 2 .d gives the results of studying the technology proposed with combined blast.

Diagrams in FIG. 2 d-1 shows furnace starting with initial conditions Cmec0=4.4% (cast iron), while diagrams in FIG. 2 d-2 show starting with Cmec0=0.3% (steel).

Time lag when transmitting control from MR-subspace to R-subspace doesn't occur with combined blast regime; the amplitude necessary for pulses interrupting carbonic fuel supply is considerably lower; undesirable changes of reduction reaction in MR-subspace for reverse ones are absent; hereby the length of transition period is preserved up to attaining carbon content in the melt ˜0.2-0.3%.

FIG. 2 .d-1 and 2 d-2 show diagrams obtained with specific furnace productivity of the order ˜2.0-2.3 t/(m² of bottom per hour). Productivity increase up to ˜2.5 t/(m² of bottom per hour) causes no changes. Iron isolation into the metal produces is equal to ˜93-95%.

FIG. 2 .d-2 shows the results of experimental furnace starting with melt preparation on the basis of steel of steel with carbon content Cmec0=0.3%. Time characteristics of the transition process obtained for metal attaining necessary carbon content (˜0.2-0.3%) after starting slightly differ from those obtained with melt preparation on the basis of cast iron. In the given case oxygen consumption for furnace starting decreases.

There is no doubt that application of technology with combined blast is more effective at high specific productivity.

With specific productivity ˜1 t/(m² of bottom per hour) it is possible to carry out operations only with upper blast; limited bottom blast can be used only when starting, and with productivity ˜2-2.5 t/(m² of bottom per hour) combined blast is necessary. It is important to note that furnace starting for specific productivity 2.5 t/m² was carried out in two stages—first for productivity 1.0-1.5 t/(m² of bottom per hour), and only when carbon content in metal was decreased specific productivity was adjusted for 2-2.5 t/(m² of bottom per hour) by increase in the flow of the charge processed.

FIG. 2 d contains the following conventional signs for curves and value dimensions

Upper Zones

-   {circle around (1.)}Fpsh=Fvsh: 0.00000125—charge consumption -   {circle around (2.)}Fpy=Fvy: 0.0000025—fuel consumption -   {circle around (3.)}Cslfo=Cvslfo: 1—FeO content in bubbled slag -   {circle around (4.)}Cslco=Cvco: 0.1—CO content in gases -   {circle around (5.)}Cslco2=Cvco2: 0.1—CO₂ content in gases -   {circle around (6.)}Cslc=Cvslc: 1—C content in slag -   {circle around (7.)}Csl3fo=Cvsl3fo: 1—FeO content at the border with     emulsion layer -   {circle around (8.)}Tsl=((Tvsl: 0.0001)+1000)—Temperature of bubbled     slag

Lower Zones

-   {circle around (1.)}Cmec=Cvmec: 1—C content in metal -   {circle around (2.)}Cme0=Cvme0* 10—oxygen content in metal -   {circle around (3.)}Fpmo=Fvmo: 0.0001—oxygen supply -   {circle around (4.)}Fvlmeo=Fvmeo: 0.0001=oxygen consumption -   {circle around (5.)}Csl3fo=Cvsl3fo: 1—FeO content at the border with     emulsion layer -   {circle around (6.)}FpO2=(Fvo2; 0.00002)—oxygen flow -   {circle around (7.)}Fme=Fvme: 0.0000025—flow of produced iron -   {circle around (8.)}Tme=((Tvme: 0.001)+1000—metal temperature

Values containing index “v” (e.g. Cvco) are shown in FIG. 2 d.

FIG. 2 e shows furnace starting by the flow of carbonic fuel supplied without pulse control.

Transition for steel production in provided by increasing oxygen and/or oxygen-containing gas supplied additionally and continuously to intermediate emulsion layer and refining layer during all the period of transition for steel production. Then, the flow of oxygen-containing gas is corrected due to furnace attaining stationary continuous operation regime for steel production.

Processing of data obtained in FIG. 2 e is carried out using table for FIG. 2 d given above.

Evaluation of the experiment conducted has shown that changes in separate parameters don't possess oscillatory components during transition process. This permits to carry out starting only with reliable operation of all the furnace parts limiting, at the same time, possibility of speedy correction of the operation regime. In case of emergency situation pulse control permits to attain the necessary correction in operation regime. Hence a very important conclusion follows: system of furnace control should permit furnace starting in both operation regimes.

According to one aspect of the present invention the method of direct continuous steel production out of iron-containing materials includes preparatory operation stages (a, b, c, d, e, f, g, h) providing for carrying out preparatory operations for furnace starting and attaining stationary regime for cast iron production, and main operation stages (i, j, k, l, m, n) for furnace transition to continuous steel output and maintaining the determined stationary regime of steel production and furnace shut-down. Such method permits to carry out adjusting of stationary regime at the intermediate stage under less stressed conditions and only then, after fulfilling main operation stages, to transit for continuous steel production.

According to another aspect of the present invention, after gaining experience, adjusting the regime for steel production can be carried out immediately.

Operation stages of furnace preparation for steel production repeat to a certain extent the stages for cast iron production described above. Complete list of preparatory and main operation stages for one-stage refining includes the following stages:

-   a) Slag melt preparation in the whole reaction space -   b) Continuous supply of oxygen-containing gas to slag melt lower     than its surface; that flow of supplied gas serves for separating     the upper melting-reduction subspace from melt; melt bubbling occurs     in the upper zone with simultaneous supply of iron-containing     material, alloying and liquefying additives and solid carbonic fuel;     determined concentration of carbonic fuel in the melt is sustained;     formation of molten slag and droplets of liquid carbon iron product     (cast iron) is provided in the upper zone by interaction between     iron-containing material, alloying and liquefying additives and     solid carbonic fuel and oxygen-containing gas; during preliminary     stage settling droplets form the lower level - level of carbon iron     product (cast iron) and the intermediate zone of calm slag. -   c) The gases formed enter the reburning zone from the upper zone of     reaction space. -   d) Carrying out discharge of liquid products of melting—slag from     the lower boundary of the intermediate emulsion layer and then from     the siphon drain of the settling zone; intermediate carbon iron     product is discharged from the lower layer on opposite side of the     furnace by means of siphon drain. -   e) Evaluation and, in case of necessity, correction of technological     regimes up to attaining the determined characteristics for     intermediate carbon iron product output. In this case temperature of     the process is fixed in the upper and lower zones, carbon content in     carbon iron product, FeO and carbon content in upper zone slag and     in the intermediate emulsion layer, as well as CO and CO₂ content in     effluent gases at the outlet from the furnace reburning zone.     Observation of determined characteristics is checked for taking into     account with the further furnace transition for steel production. -   f) Evaluation of stability in maintaining determined characteristics     during several 6-hour shifts and taking the decision on     acceptability of proceeding to main operation stages of direct steel     production. -   g) Starting the supply of oxygen and/or oxygen-containing gas and/or     inert gas into intermediate emulsion and refining layers, thus     creating there the conditions for intensive turbulent-diffusion     transfer of iron oxides from the upper zone to the lower refined     metallic layer. In this case oxygen isolated during decomposition of     iron oxides entering the intermediate and lower layers interacts     with carbon in carbon-iron intermediate product droplets and, thus,     provides for the start of carbon iron intermediate product refining.     Refining is practically carried out simultaneously in the     intermediate emulsion layer and in refining layer. -   h) According to the given aspect of the present invention, method of     furnace transition for steel production is proposed by using the     original method of refining process intensifying protected by the     present application. Let us orient for method of combined blast due     to which supply of limited bottom blast is initiated.

The value of the bottom blast flow should comprise ˜10-20% of the total oxygen flow entering for refining.

-   i) The most important part of the operational program for starting     continuous steel production is the technology of oxidizing the     refined metal in the furnace up to the level of determined     characteristics.

This task can be provided for in the regime of pulse control by a correlated choice of a regime of pulse interruption (increase, decrease) in charging solid carbonic fuel, structure of charging and corresponding quantitative characteristics of the processed charge flow and the oxygen-containing blast flow into the intermediate emulsion layer, refining layer and bottom blast. Hereby all the chosen values for gas flows supplied to the furnace, except for blast flow into emulsion layer, remain fixed during all the period of transition for steel production.

Let us specify some methodical regulations of the present operation stage.

It is impermissible to surpass the pulse length and to decrease intervals between pulses as specified in accordance with determined characteristics of steel production as these violations can cause higher CO₂ concentration in the upper zone and termination of reduction process leading to complete disruption in furnace operation.

In case an increasing continuous delivery of oxygen-containing gases is used for furnace starting for steel production instead of pulse control, it is important not to disturb the process hydrodynamics. Disturbances in hydrodynamics of the process can cause the necessity of speedy correction of technological regimes, these corrections are rather difficult to attain without pulse control.

-   j) With shortage of reaction gases formed initially in the     intermediate layer, oxygen and/or oxygen-containing and/or inert gas     supply and/or their mixture is increased into the intermediate     emulsion layer through side and/or bottom tuyeres. -   k) After evaluating the accomplishment of the determined     characteristics in relation to carbon and admixtures content in the     steel produced in the process of furnace transition to continuous     steel production, average consumption of carbonic fuel supplied,     alloying or liquefying additives and/or flows of additionally     delivered oxygen or oxygen-containing gases through side and/or     bottom tuyeres into intermediate emulsion layer “slag-refined     metal-gas” and/or lower refining melt, is being corrected to meet     the determined characteristics. -   l) Special observation for carbon, oxygen and admixtures content in     produced metal and for carbon and iron oxides content in slag     obtained is carried out continuously during steel production by     supplying given flows of iron-containing material, necessary slag     components, average flow of solid carbonic fuel and determined flow     of oxygen-containing gas with simultaneous discharge of molten metal     and slag from reaction space. -   m) Decision on the necessity of final correction for the basic     (intermediate) technological regime of steel production is taken by     comparing the determined characteristics in claim 1 concerning     quality of steel produced and slag losses with the determined     characteristics. -   n) Regime of furnace shut-down will be discussed later by giving     definite examples.

Let us study changes which are to be introduced in case the operation of steel refining is to be performed according to two-stage system.

With two-stage refining preparatory operation stages a, b, c, d, e and f remain without any changes.

Operation stages h and i performed during furnace transition for direct steel production are carried out in turn—at first for the first stage (when charging) and then—for the second, final stage (before metal discharge).

Operation j is performed according to the method described above but only for the first stage of refining. In this case it is desirable to lift the vertically moved tuyere in the second refining stage.

Operation j is repeated for the second stage of refining. Hereby it is also desirable to lift the vertically moved tuyere.

Operation k is conducted simultaneously for the first and second stages.

When performing operation 1, in contrast to technique of this stage performing for one-stage variant, final regulation of carbon and admixtures content in steel produces is carried out by vertical or side tuyeres.

Operations m and n are carried out simultaneously for both stages.

Adjusting of the technological process of steel production with an external installation for carrying out the second stage of refining is carried out in the same stages as for the two-stage refining. Operations planned for the second stage are to be carried out in the external installation.

By performing the operation stages mentioned above complete technological preparation, adjustment and starting the process of direct steel production is fulfilled and continuous exploitation starts.

So, it is expedient to underline that FIG. 2 c illustrates experimental certification of the possibility of furnace transition from the regime of intermediate product (cast iron) production for the regime of steel melting using “upper blow-down” by sending pulse interruptions in the flow of solid carbonic reducer (line 1 in FIG. 2 c—lower layer).

FIG. 2 d illustrates two examples of transition for the furnace with “combined blow-down” to steel production from different initial conditions. In the first example cast iron was prepared in the furnace during preliminary stage (line 1 in FIG. 2 d-1—lower layer), and in the second example steel was prepared with Cmec0=0.35%. (line 1 in FIG. 2 e-2—lower layer).

FIG. 2 e shows starting the furnace without pulse controls for the case when cast iron has been prepared in the lower zone for furnace starting (line 1 in FIG. 2 e-1—lower layer) and for the case when steel with carbon content 0.3% was used for starting (line 1 in FIG. 2 e-2—lower layer).

Regime of steel production with determined carbon content 0.0024% has been provided by changes in the flow of oxygen supplied into intermediate emulsion layer and lower refining layer.

Further, let us consider the device (installation) for realizing the methods of direct steel production described.

It is supposed that the installation developed is to process finely grained iron-containing material. The installation discussed represents a furnace for direct steel production according to FIG. 3 and, correspondingly, has single melting-reduction space 6 situated in the upper zone of the melt above level H2 in shaft 13, intermediate zone 7 situated in the lower part of shaft 13 between the melt levels H4 and H2, reservoir 11 with bottom 12 destined for forming lower zone for refining intermediate carbon iron product 8 from bottom to level H4. Height of the working space from bottom to arch is designated as H1.

Furnace complex comprises feeders for charging iron-containing material 1, alloying and liquefying additions, solid carbonic fuel 2 through pipe 14 into melting space of the upper zone, tuyeres 15 at height H3 for supplying oxygen or oxygen-containing gas 3 into reburning zone 9, tuyeres 16 at height H2 for supplying oxygen-containing gas or this gas mixture with inert gas 10 and fine-grained carbonic fuel 38 with separate supply of fine and coarse fractions into upper melting-reduction zone, special tuyeres 16′ for delivering small fractions of solid carbonic fuel in the flow of inert gas, additional tuyeres 17 at height H4 for supplying oxygen, oxygen-containing and/or inert gas 4 into intermediate emulsion layer “slag-refined metal-gas” (with the aim of increasing transfer of iron oxides into that layer and oxygen from that layer into refining subspace, reagent supply and refining process intensifying) bottom tuyeres 17′ for intensifying refined metal agitation and oxygen and/or inert gas 5 supply into the lower refining zone.

Refining reservoir 11 with bottom 12 is fitted with channel 22 for steel output made in the wall of refining reservoir and channel 23 situated on the opposite side and destined for discharging slag and metal taken with it into settling zone 21 (wherefrom slag is removed through siphon drain and metal is returned to refining subspace. Then the metal enters through the second siphon drain into external installations for treating steel obtained with the aim of processing steel for meeting the determined characteristics).

Gas duct 24 serves for technological gases output from the shaft. (FIG. 4)

Refining reservoir and shaft can be made round or rectangular in shape in horizontal cross-section; all tuyeres 15, 16 and 17 are installed at corresponding levels of side walls of shaft 13 and reservoir 11. Bottom tuyeres 17′ are installed on the whole area of bottom 12 at a certain distance from one another.

With the aim of decreasing refractory materials consumption and increasing the period between furnace overhauls, part of the furnace shaft as well as walls and refining reservoir bottom are to be cooled. Hereby jackets with water cooling are installed on shaft surfaces to be cooled and slag lining is formed on their inner walls preventing heat losses.

With steel production during refining the metal will be boiling in the lower zone. That's why jackets used for protecting refractory walls at the slag level cannot be used for protecting walls of boiling metal bath. Slag lining formed on walls of plates with heat tubes filled with molten high temperature filler is used in the given design for protecting refractory brick in reservoir 11 and bottom 12.

It is to be noted that thermal tubes solve only the problem of decreasing the firebrick lining; due to the fact that metal is boiling (bubbling) during refining, prolonged resistance of firebrick lining without special protection by metal lining shouldn't be anticipated. FIG. 3 shows thermal tubes 20 and outer thermal exchangers 19 through which cooling liquid 18 is flowing.

In a number of cases two stage refining may be necessary due to occurrence of some phenomena caused by physico-chemical composition of iron-containing ores to be processed and/or special requirements to steel produced. FIG.

5 shows a modification of the installation described above for providing condition for carrying out two stage refining of carbon iron product with the second stage being situated out of the outer boundary of the reaction space (FIG. 5 a) or in the form of a separate external block (FIG. 5 b) wherein melt enters from the furnace )FIG. 4) after the first refining stage or even carbon iron product (cast iron) simply reduced. Variant of the installation in FIG. 5 a to be proposed for two stage refining differs from the basic one (FIG. 4) only by the presence of two subsequent refining reservoirs separated from each other by a partition 25 (FIG. 5 a), by the possibility of changing slag and creation of partial counter-current “refined metal—slag” by means of butt end tuyeres 27 (FIG. 5 a).

In this device possibility of using movable vertical tuyere 26 for oxygen or oxygen-containing gas supply to the second refining reservoir is provided for with the aim of increasing reliability in meeting technological requirements to the quality of steel produced and for dividing the second refining stage into two zones.

External block for one-stage refining in FIG. 5 b in complex with the installation in FIG. 4 solves the same problem as an installation in FIG. 5 a.

Block in FIG. 5 b is developed on the basis of the known device for continuous cast iron refining IRSID. The difference lies only in the fact that the block described in the complex according to the present patent performs only the second stage of continuous refining with initial conditions principally different from conditions of IRSID installation operation; only under emergency conditions when basic block (FIG. 4) produces only cast iron, block (FIG. 5 b) is used for refining operation on the whole.

Metal in the device according to FIG. 5 b enters continuously from furnace in FIG. 4 through charging inlet 28 in the external block. Cold additives are charged through inlet 29. Oxygen or oxygen-containing gas flow 30 is supplied through vertical movable tuyeres 26 (FIG. 5 b shows one) or by means of tuyeres installed on side walls.

Refined metal is discharged through siphon drain 31, slag is discharged through outlet 32; effluent gases are removed along pipe 33 and gas duct of the main furnace in FIG. 4 (not shown in FIG. 5 b). Refining block in FIG. 5 b can be divided into two separately controlled zones.

Application of installations in FIG. 5 a and FIG. 5 b for conducting the second stage of refining permits to obtain high quality steel.

The description of the device for direct steel production should be incomplete without describing two main units—unit for supplying gas-dust mixture with solid reagents into intermediate layer for increasing refining quality of carbon iron product and the unit of increasing exploitation reliability of the partition separating reservoirs for the first and second refining stage.

FIG. 6 a shows a special side tuyere 17 for supplying gas phase 4 with necessary reagents 34, e.g. powdered lime, into intermediate emulsion layer and refining layer.

Metal boils in reservoir 11 with bottom 12 which practically serve as a lower zone for main device of direct steel production in FIG. 3, isolating carbon oxide CO in this case enters intermediate emulsion layer 6.

To increase exploitation reliability of partition 35 (FIG. 6 b) method of partition cooling with the aim of metal lining formation on its wall by means of special heat tubes 36 with high temperature filler 37 is being proposed. Heat tubes 36 are mounted in the partition from the central axis in the direction of side walls of the furnace to provide for the desired direction of the flow of high temperature carrier flow in the direction of cold ends which are outside the furnace; cooling of the said heat tubes is provided by external co-current heat exchangers 39 with heat carrier 40. Heat tubes are inclined to the side of the partition central axis for not more than 15°, this inclination being sufficient for returning condensed heat carrier into the hot zone of heat tubes.

Three postulates of the invention proposed are explained by definite examples of its embodiment and are followed by real diagrams in FIGS. 7, 8 and 9.

EXAMPLE 1

When refining carbon iron product obtained in the upper zone, it is very important to carry out intensive agitation of the melt in the lower zone. Gas flows entering the refining subspace from intermediate emulsion layer and bottom blast provide for melt agitation by bubbling. However, upper and bottom blasts possess several balance limitations.

The present application studies agitation of metal in the lower refining zone by means of short pulse interruptions in solid carbonic fuel supplied to the furnace as one of the operational methods of attaining the goal.

FIG. 7 a shows diagrams of state variables and flows of charge processed, oxygen-air blast and pulse interrupted solid carbonic fuel supplied to the furnace. Interruption is carried out with one hour interval, pulse amplitude equals to ˜0.9 from supplied flow Fpy, and length of pulse is only ˜0.05 h.

As diagrams show, such short interruptions in the fuel supply are sufficient for exciting considerable oscillations in the main refining reaction.

It is known that during oscillatory regime rates of a number of reactions considerably increase. Characteristics of oscillations occurred weren't evaluated in the scale of FIG. 7 a due to high oscillation frequency. FIG. 7 b presents part of this diagram in another time scale when all the X-axis scale represents one second.

After processing the diagram of state variables changes with time, it was obtained that the period of forced oscillations in the main refining reaction makes ˜0.2 sec, i.e. pulse interruption of fuel supply permits to obtain oscillatory process of the chemical reaction conducted with frequency of about 5 Hz along the whole volume of the metal refines in the lower zone. Conventional designations of FIGS. 7 a and 7 b are given in page.

EXAMPLE 2

Approach to applying the proposed method to direct steel production has been studied above in detail, the main attention having been paid to the technology of attaining direct steel production.

The present example studies the technology of temporary, rather long furnace shut-down and its further start-up for the previous regime of direct steel production. In this case we discuss not the complete shut-down for capital repairs, but shut down for the period of 6 hours for conducting current repairs.

FIG. 8 a presents changes in state variables and flows of charge, oxygen-air gas and fuel supplied to the furnace in the process of carbon iron product production (from 0 to 1 hour), starting steel production (from 1 to 5 hours), steel production (from 5 to 6 hours), 6 hour shut-down with termination of loading the charge processed and decrease for 50% in fuel supply and oxygen-containing gas (from 6 to 12 hours); then, subsequent furnace start-up for stationary regime of steel production from initial conditions of the end of 6-hour shut-down for three additional hours is shown in FIG. 8 b.

During first 6 hours (FIG. 8 a) start-up of the furnace according to the scheme described above is carried out. Attaining the given stationary regime takes about 5 hours, and the 6^(th) hour the furnace is working in the stationary regime.

From the time of shut-down—6 o'clock (according to FIG. 8 a)—the furnace was not functioning for 6 hours. During that time fuel burning continued with lowered load, reduction process has practically stopped, however, C content in the metal bath didn't increase. The only thing to be mentioned consists in the fact that immediately after the shut-down high increase in oxygen content in the metal occurred up to complete saturation, possibly due to the fact that with the ratio chosen consumption of fuel supplied couldn't be balanced with the necessity in oxygen for burning and CO isolation usually consumed for reduction.

However, during the 4^(th) hour of shut-down (at 10 o'clock in FIG. 8 a) oxygen concentration started to fall.

Start-up of the furnace after shut-down is shown in FIG. 8 b (continuation of FIG. 8 a with new time count). Flows of fuel and oxygen-containing gas were simultaneously increased up to stationary regime taken and immediately after that loading of charge processed was started.

In FIG. 8 b behavior of state variables in upper reduction zone (lines 1-8) and lower refining zone (lines 1, 3, 4, 6, 7, 8) is shown beginning with t=0. State variables designated by these numbers immediately attained the same values which they had before furnace shut-down. The only peculiarity of the start-up regime after prolonged shut-down consisted in the fact that vigorous reaction of metal refining which goes for about 0.75 h (hatched area in FIG. 8 b) up to the time when oxygen concentration drops to the level corresponding to continuous stationary regime.

According to FIG. 8 b it occurs at 0.65-0.7 h according to the diagram scale. This phenomenon is not repeated later.

EXAMPLE 3

This example studies the problem of effective organization at the start-up process when the furnace carries out transition from carbon iron product production for steel production. Attentive studying of the start of the process in FIG. 2 b for both examples given above, shows that the start of the transition process in refining zone lags behind from the moment of first pulse application: with two pulse start-up for 0.45 h, with three pulse start-up for 0.6 h, in some cases the time lag was more than 1 h (FIG. 9 a). Time lag described prolongs starting time and, what is more important, highly complicates operative control for start-up operations and process control under conditions of normal exploitation.

Due to that, the application for the patent provides for the variant of additional oxygen supply for the time of all the furnace operation during furnace transition for steel production by means of bottom blow-down in case it has not been installed beforehand.

FIG. 9 gives the results of testing the patented forestalling unit. FIG. 9 a shows changes in variables during furnace transition without forestalling unit, and FIG. 9 b shows the same but with this unit.

According to the results of tests it is seen that time lag at the start of the transition process has been completely eliminated with additional oxygen supply into the lower zone.

Conventional signs of curves and value dimensions taken for all the examples studied in FIG. 7, 8, 9:

Upper Zones

-   {circle around (1.)}Fsh=Fvsh: 0.000005.—charge consumption -   {circle around (2.)}Fpy=Fvy: 0.00001—fuel consumption -   {circle around (3.)}Cslfo=Cvslfo: 1—FeO content in bubbled slag -   {circle around (4.)}Cslco=Cvco: 0.1—CO content in gases -   {circle around (5.)}Cslco2=Cvco2: 0.1—CO₂ content in gases -   {circle around (6.)}Cslc=Cvslc: 1—C content in slag -   {circle around (7.)}Csl3fo=Cvsl3fo: 1—FeO content at the border with     emulsion layer -   {circle around (8.)}Frzd0=Fvrzd: 0.000005—oxygen gas flow

Lower Zones

-   {circle around (1.)}DCmec=Cvmec: 1—C content in metal -   {circle around (2.)}Cme0=Cvme0: 5—oxygen content in metal -   {circle around (3.)}Fpmo=Fvmo: 0.00004—oxygen supply -   {circle around (4.)}FV1meo=Fvmeo: 0.00004=oxygen consumption -   {circle around (5.)}Csl3fo=Cvsl3fo: 1—FeO content at the border with     emulsion layer -   {circle around (6.)}Frzg0=Fvrzg: 0.000005—oxygen gas flow -   {circle around (7.)}Tme=((Tvme: 0.0001)+1000)—metal temperature -   {circle around (8.)}Fme=Fvme: 0.00001—flow of produced iron

Values containing index “v” (e.g. Cvco) are shown in diagrams FIG. 7., 8., 9.

Technology of data processing is carried out using the table given for FIG. 2 d. 

1. Process of direct continuous steel production out of iron-containing materials, present in the form of a liquid refined layer and a liquid slag layer containing iron oxides and admixtures to be processed, comprising the following stages: Provision of a single reaction space by the said layer of refined metal situated under the layer of the liquid slag which contains iron-containing materials to be processed and droplets of reduced metal so that an intermediate emulsion layer “slag-melted metal-gas” is designated in between the said layers, continuous supply of iron-containing materials into reaction space including alloying and liquefying additives, oxygen containing blast and solid carbonic fuel supply, as well as continuous removal of liquid metal, slag and effluent gases from the reaction space, supply of the flow of oxygen and/or oxygen containing gas and/or inert gas and/or their mixture into intermediate emulsion and refining layers, creating conditions in emulsion layer for intensive turbulent-diffusion transfer of iron oxides and reduced metal droplets contained in slag layer into intermediate emulsion layer, hereby providing the interaction of oxygen isolated during iron oxides decomposition and the oxygen supplied to the emulsion and refining layers—with the carbon from reduced iron for providing the process of refining which occurs simultaneously in the intermediate emulsion and refining layers, intensifying transfer of metal droplets and carbon oxide from the slag layer and the progress of refining process due to carbon oxide isolated during refining and leading to refined metal boiling (bubbling), whereas the intermediate emulsion layer and the layer of refined metal function together as a single dynamic system with positive feedback having at least two regions of equilibrium conditions—“cast iron” and “steel”, Provision of the preliminary determined contents of dissolved carbon, oxygen and admixtures in the said refining layer and, consequently, in the steel produced—in the desired dynamic system operational regime, in equilibrium region “steel” which is realized at the start-up by forming pulse/continuous/controls for supplying solid carbonic fuel, oxygen and/or oxygen-containing gas and/or oxygen dioxide and/or air and/or inert gas and/or mixture thereof, as well as by control for the flow of charge processed, Stabilization of technological regime under the conditions of normal continuous exploitation by controls mentioned earlier permitting to maintain the correspondence of the steel quality produced to the determined characteristics.
 2. Process, according to claim 1, wherein the layers of the said liquid refined metal and slag are created by means of coke-free reduction of iron and some admixtures out of iron-containing materials to be processed which are chosen from the group containing, in particular, ground iron-containing ores, iron-ore concentrates, iron-containing waste, iron-containing scrap.
 3. Process, according to claim 1, wherein the said refining includes decarburization of liquid metal and removal of definite admixtures.
 4. Process, according to claim 2, wherein coke-free reduction is realized in the said single reaction space.
 5. Process, according to claim 1, wherein the said layer of refining metal has the desired content of carbon and admixtures.
 6. Process, according to claim 1, wherein the desired carbon content in the metal produced within the limits of ˜0.2-2.0% is provided by realizing one of the existing dynamic system equilibria for refining carbon iron product.
 7. Process, according to claim 1, wherein high frequency oscillations in metal layer to be refined are excited for intensifying some chemical reaction, e.g., by means of pulse interruptions in solid fuel supply having pulse length T

M=˜(0.01-0.5) h and amplitude ˜(0.1-0.8)*A

M, where A

M.=Fpy—flow of solid carbonic fuel supplied.
 8. Process, according to claim 1, wherein the given oxygen content in refined metal is provided by oxygen coming from iron oxides decomposition and, in case of shortage, by additional blowing according to schemes of upper or combined blow-down through side and/or bottom and/or vertical tuyeres.
 9. Process, according to claim 8, wherein the additional gas supplied contains up to 99.5% of oxygen.
 10. Process, according to claim 9, wherein the moment of attaining the desired operational regime is determined according to admixtures content in steel, after which oxygen supply by additional tuyeres is considerably decreased, and transition for operational regime of stationary control is carried out.
 11. Process, according to claim 9, wherein in case of stable progress of the given operational regime complete termination of oxygen supply by additional tuyeres is carried out.
 12. Process, according to claim 10, wherein in case of terminating oxygen supply by additional tuyeres, transfer of these tuyeres operation for inert gas supply for maintaining the attained operational regime is carried out.
 13. Process, according to claim 12, wherein oxygen content of up to 75% is provided for in the inert gas.
 14. Process, according to claim 1, wherein the said layer of refined metal has oxygen content in the desired range of 0.001-0.5%.
 15. Process, according to claim 1, wherein the said quick transfer of iron oxides and reduced iron droplets from slag layer into intermediate emulsion layer “slag-molten metal-gas” as well as from that layer into the refined metal layer is provided by supply of oxygen-containing gas and reaction gases entering from refining layer by means of bubbling the slag melt, turbulent diffusion and changes in interphase surface of the intermediate emulsion layer, as well as, in case of necessity, also by supplying oxygen-containing blast and/or mixture of oxygen and inert gas and/or inert gas by additional side, bottom or vertical tuyeres.
 16. Process, according to claim 1, wherein the stage for controlling the desired content of carbon and admixtures in steel produced as well as iron oxides and carbon in slag attaining intermediate emulsion layer “slag-molten metal-gas” is carried out.
 17. Process, according to claim 16, wherein the desired iron oxides content in slag is provided within the limits of ˜0.1-15%.
 18. Process, according to claim 16, wherein the said control includes discrete-continuous content determination, in particular, oxygen, carbon and admixtures content in slag, carbon and iron oxides content in slag leaving the reactor, CO and CO₂ content in furnace effluent gases.
 19. Process, according to claim 16, wherein the said control includes regulation of composition and quantity of iron-containing product supplied, carbonic fuel and other incoming flows, hereby solid carbonic fuel is delivered whole into upper bubbled slag layer from above.
 20. Process, according to claim 16, wherein the said control includes regulation of composition and quantity of iron-containing product supplied, carbonic fuel and other incoming flows, hereby small fractions of carbonic fuel are sieved from the main fuel flow and supplied in the flow of inert gas through special tuyeres into slag layer.
 21. Process, according to claim 1, wherein, in case of necessity, for attaining the necessary carbon and admixtures content in steel produced, the reaction subspace of refining layer is divided at least for two zones functioning in series in relation to carrying out separate operation stages in refining the steel produced.
 22. Process, according to claim 18, wherein, in case of necessity, the last operational stages of refining the steel produced are carried out outside the reaction space with supplying the intermediate carbon iron product refined from that space.
 23. Device for direct continuous one-stage steel production out of iron-containing materials comprising: inlets for continuous supply of all the previously determined input products, reservoir for one-stage refining of carbon iron product supplied with upper and/or combined blow-down, at least one tuyere connected to the desired region inside the installation for delivering oxygen containing gas and/or inert gas and for providing preliminary determined carbon, oxygen and admixtures content in the refined layer of metal in relation to the given working regime, panels of heat tubes with high temperature fillers for lining walls, bottom and reaction reservoirs partition made of firebricks which are protected by the said panels from strong wear due to practically continuous metal boiling (bubbling) under conditions of normal exploitation, outlets for continuous removal of liquid slag and metal from reaction space and metal delivery, in case of necessity, for external processing and refining up to the determined characteristics.
 24. Device for direct continuous multistage steel production, comprising: blocks and units of the device for one-stage refining characterized by the fact that the reaction space for refining process permitting to realize upper and combined blow-down is formed by at least two reservoirs providing for carrying out the process at least in two stages, application of more than one reservoir for refining within reaction space provides for the possibility of mounting at least one vertical movable tuyere for oxygen and/or oxygen-containing gas supply beginning with the second longest reservoir, additional atomizers at the furnace butt end near metal output at the slag level are installed with provision of even partial counter-current “slag-metal”, siphon drains connected with the main furnace space through outlets for continuous removal of produced steel and slag, pipe for connecting with effluent gases from the first process stage, steel supply, in case of necessity, for external processing and refining according to determined characteristics.
 25. Device for direct continuous multistage steel production, comprising: blocks and units for one-stage refining with upper and/or combined blow-down, external refining block comprising: reaction space with a reservoir for at least one refining stage, inlet for continuous metal supply from the device for one-stage refining or intermediate heated reservoir, inlet for scrap loading and other slag forming agents, at least one vertical movable tuyere for oxygen and/or oxygen-containing gas supply, reservoir for slag-metal emulsion separation, siphon drains connected with the main furnace space through outlets for continuous removal of produced steel and slag, pipe for effluent gases removal and their uniting with the effluent gases from the first process stage, trough for steel delivery, in case of necessity, for external processing and refining according to determined characteristics. 